Exploring, drilling, completing, and operating hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well access, monitoring and management throughout its productive life. Ready access to well information as well as well intervention may play critical roles in maximizing the life of the well and total hydrocarbon recovery. As a result, downhole tools are frequently deployed within a given hydrocarbon well throughout its life. These tools may include logging tools to provide well condition information. Alternatively, these tools may include devices for stimulating hydrocarbon flow, removing debris or scale, or addressing a host of other well issues.
The above noted downhole tools are generally delivered to a downhole location by way of a well access line, such as a wireline cable, drill pipe, coiled tubing, slickline, etc. Regardless, once positioned downhole at the end of the well access line, a well application may be employed by such a tool. A winch or other appropriate surface equipment may then be employed to withdraw the well access line and tool from the well. However, in many cases the tool may be stuck in place downhole. This may be due to the presence of an unforeseen obstruction, unaccounted for restriction, differential sticking of the tool against the well wall, a malfunctioning tractor, or a host of other reasons. Indeed, with the presence of increasingly deeper and more deviated wells, the likelihood of a downhole tool becoming stuck merely due to the depth and architecture of the well alone is increased.
Regardless of the particular reason for the sticking of the downhole tool, continued efforts to withdraw the line may lead to significant line or tool damage. Additionally, the risk of breaking the line at some intermediate location and leaving potentially several thousand feet of line in the well may be of concern. Thus, in order to help avoid a circumstance in which the line is broken, a release mechanism is generally incorporated into a head which serves as the connection between the downhole tool and the well access line. In this manner, surface equipment such as the noted winch, may continue to pull the line out of the well, leaving only the downhole tool and part of the head behind. A subsequent fishing application may take place in order to retrieve the tool and head.
A common release mechanism involves incorporating a “weakpoint” or separable housing into the noted head. The weakpoint is held together by at least one tensile stud. However, it may be broken once a predetermined load is applied. So, for example, consider a tensile stud providing a weakpoint of about a 2,000 lb. threshold to the head, which is in turn coupled to a tool that has become stuck in the well. In such a case, the head will break, freeing the well access line from the well once a pull exceeding about 2,000 lbs. is achieved.
Unfortunately, employing a tensile stud incorporated into the housing of the head requires that the tensile stud and load threshold be predetermined. That is, the most effective size of the threshold to be incorporated into the logging head may be dependent on a variety of factors. For example, the load threshold of the well access line itself, the potential sticking depth of the tool, and the overall size of the downhole toolstring may all play a role in determining the most effective tensile stud to use. As a practical matter, this means that a couple of different heads and between about 10 and 20 different tensile studs of different load thresholds, or “weakpoint” values, are generally made available at the oilfield. In spite of this large amount of equipment, only one of the tensile stud/head combinations is ultimately incorporated into the overall line assembly.
The inability to tailor a weakpoint value in a practical manner for a given head on-site, may lead to the compromising of operations. For example, often times, in an effort to minimize the amount of equipment brought to the site, an operator will bring fewer tensile studs to the site leaving fewer weakpoint values available. However, this runs the risk that the proper logging head will be unavailable on site adding significant delay to the operation or worse, the employment of an improper logging head of potentially catastrophic consequences. At a minimum, the operator is left with the option of hauling a significant number of unutilized studs to the site or risk the possibility of hundreds of thousands of dollars in lost time for failure to do so.